Bella, F., R. Bella, P. F. Biagi, M. Caputo, G. Della Monica, A. Ermini, W. Plastino, and V. Sgrigna. “Artificial and Natural Electromagnetic Signals Revealed During Two Years in the Amare Cave (Central Italy)”. Annals of Geophysics, vol. 37, no. 5 Sup., Nov. 1994, doi:10.4401/ag-4161.